Fungal Composition and Diversity of the Tobacco Leaf Phyllosphere During Curing of Leaves

Abstract

Rhizopus oryzae causes tobacco pole rot in China during tobacco flue-curing. Fluecuring is a post-harvest process done to prepare tobacco leaves and involves three different stages: the yellowing stage has the lowest temperatures and highest humidity, then the color-fixing stage has higher temperatures and medium humidity, and finally the stem-drying stage has the highest temperatures and lowest humidity. In this study, fungal culturing and IonS5XL high-throughput sequencing techniques were used to reveal the fungal community of the petioles and lamina of tobacco leaves infected with pole rot during flue-curing. A total of 108 fungal isolates belonging to 6 genera were isolated on media. The most common fungal species isolated was the pathogen, R. oryzae, that was most often found equally on petioles and laminas in the color-fixing stage, followed by saprotrophs, mostly Aspergillus spp. High-throughput sequencing revealed saprotrophs with Alternaria being the most abundant genus, followed by Phoma, Cercospora, and Aspergillus, whereas Rhizopus was the tenth most abundant genus, which was mostly found on petioles at the yellowing stage. Both culturable fungal diversity and fungal sequence diversity was higher at stem-drying stage than the yellowing and color-fixing stages, and diversity was higher with leaf lamina than petioles revealing that the changes in fungal composition and diversity during the curing process were similar with both methods. This study demonstrates that the curing process affects the leaf microbiome of tobacco during the curing process, and future work could examine if any of these saprotrophic fungi detected during the curing of tobacco leaves may be potential biocontrol agents for with pole rot in curing chambers.

Effects of ecological environment and host genotype on the phyllosphere bacterial communities of cigar tobacco (Nicotiana tabacum L.)

“…As shown in Figure 1 , rarefaction curve of each sample tended to approach the plateau phase, when the amount of sequencing data reached approximately 40,000. This indicated that the number of sequences in these samples was sufficient to represent the bacterial composition (Chen et al., 2020 ).…”

“…In addition, genetic background of tobacco might have certain effects on the diversity and structure of bacterial community in phyllosphere, possibly by leaf surface properties or jasmonic acid/γ-aminobutyric acid signaling pathway (Chen et al, 2020;Vorholt, 2012). Kim et al (2012) observed that the similarity of phyllosphere bacterial community among these tree species was determined by the host plant phylogeny and more similar communities in closely related host plants.…”

“…In addition, genetic background of tobacco might have certain effects on the diversity and structure of bacterial community in phyllosphere, possibly by leaf surface properties or jasmonic acid/γ‐aminobutyric acid signaling pathway (Chen et al., 2020 ; Vorholt, 2012 ). Kim et al.…”

“…Genotypes, geographical location, and land-use could affect the community of Proteobacteria; normally, we can see the significant different community composition among meadows and mown pastures (Wellner et al, 2011). Tobacco (Nicotiana tabacum L.) is an important agricultural nonfood crop and the main raw material of tobacco commodities worldwide (Chen et al, 2020;Lisuma et al, 2020). It is widely cultivated in South China, such as Hainan and Sichuan (Tang et al, 2020;Yuan et al, 2016;Zhao et al, 2007).…”

“…Tobacco ( Nicotiana tabacum L.) is an important agricultural nonfood crop and the main raw material of tobacco commodities worldwide (Chen et al., 2020 ; Lisuma et al., 2020 ). It is widely cultivated in South China, such as Hainan and Sichuan (Tang et al., 2020 ; Yuan et al., 2016 ; Zhao et al., 2007 ).…”